The usage of sheet molding compositions (SMCs) and bulk molding compositions (BMCs) have expanded as the ability to improve surface finish properties and physical properties such as strength of articles formed from the cured thermoset resins have improved. However, in spite of the improvements in these materials, the production of coated or multilayer molding composition articles so as to adhere thermoplastics and inorganic coatings has proven a difficult task owing to high molding composition article surface energies as measured by water droplet contact angle. The high surface energies manifest in incomplete and poor adhesion between the SMC or BMC and the overlayers. While the quality of surface finish and bonding properties are modified by the inclusion of a low profile additive such as a thermoplastic or elastomer into the thermoset resin composition, overlayer adhesion remains a problem. While improvement of interfacial adhesion has been achieved with base material formed of thermoplastics, elastomers, fluoropolymers through flame treatment and/or plasma treatment, extension of these results to SMC and BMC has proven difficult to implement on a production scale.
Surface properties of SMC's and BMC's have previously been modified through rendering the thermoset cured article electrically conductive to a sufficient extent to allow for powder prime coating, as detailed, for example in U.S. Pat. No. 7,655,297; yet numerous coatings still have poor adhesion to cured SMC or BMC.
Thus, there exists a need for a process to treat a cured thermoset SMC or BMC article to promote adhesion of an overlayer thereto. Such an overlayered material with strong adhesion between SMC or BMC article and the overlayer are suitable for a variety of applications previously unavailable to SMC or BMC materials including those in the fields of automotive, aerospace, and architectural structures.